A blood test may be capable of identifying the risk of autism years before physical symptoms appear, researchers have said.

The study, published by New York’s Rensselaer Polytechnic Institute, is the first of its kind to detect autism before identifying behavioural changes.

The blood test works by identifying altered levels of FOCM (folate-dependent one-carbon metabolism) and TS (transulfuration) – both associated with autism.

The researchers claim that the test could correctly classify 97.6 per cent and 96.1 per cent of the autistic and neurotypical children tested respectively.

“The method presented in this work is the only one of its kind that can classify an individual as being on the autism spectrum or as being neurotypical,” said lead author Professor Juergen Hahn.

“We are not aware of any other method, using any type of biomarker that can do this, much less with the degree of accuracy that we see in our work.”

The scientists say that early diagnosis of autism could avoid years of distress for children who are in need of specialist treatment.

Professor Hahn added: “The number of diagnosed cases of autism spectrum disorder (ASD) has increased dramatically over the last four decades.

“However, there is still considerable debate regarding the underlying pathophysiology of ASD.”

Autism affects around 1 in every 100 people, or about 700,000 people across the UK.